The present invention relates to an image processing method and apparatus, a recording medium and an imaging apparatus, and more particularly to an image processing method and apparatus for removing noise of an image, a medium for recording a program for a computer to perform such an image processing function, and an imaging apparatus comprising such an image processing apparatus.
In a magnetic resonance imaging (MRI) apparatus, an object to be imaged is carried into an internal space of a magnet system, i.e., a space in which a static magnetic field is generated; a gradient magnetic field and a high frequency magnetic field are applied to generate a magnetic resonance signal inside the object; and a tomographic image is produced (reconstructed) based on the received signal.
In order for an observer to view a fine structure in the tomographic image in more detail, filtering is performed to remove noise in the image. Although the filtering is basically low-pass filtering, since the sharpness of the image is lowered by using the low-pass filtering alone, filtering with an additional process for preserving the sharpness is employed.
The filtering in combination with the process for preserving the sharpness involves defining in a plurality of modes a local region containing a pixel of interest in an original image, calculating the variance of pixel values for the local region in every mode, obtaining an average value of pixel values of the region having the minimum variance, and using the average value as a new pixel value for the pixel of interest.
Since such filtering, however, obtains the variances of pixel values for the local region in all the modes and thereafter extracts the minimum variance, the processing speed of the filtering is low.